Many automotive refinishing and light industrial paints comprise multiple components. These are called plural component paints. Sometimes they are referred to as “n”K paints, that is, 2K for a two component paint, 3K for a three component paint, and so on. The components typically include, for example, a base component, such as, for example, a clear coat, an activator and a reducer.
These components are mixed in various ratios to obtain the final sprayable product. The ratios are typically measured and mixed by hand or by using expensive metering and pumping equipment. Once the activator is added, the sprayable pot life is short, for example, only one to three hours. Therefore, any excess mixed product becomes waste. The mixed product is expensive, for example, $40.00 U.S. per quart (about $42.00 U.S. per liter).
Painters using gravity- or suction-feed cup-type spray guns measure and mix the product by hand. Mixing too much, mixing the wrong ratio, and cleaning the gun generate waste. Painters using pressure-feed guns with remote paint tanks typically use expensive, for example, $5000-$15,000 U.S., metering and pumping equipment. This equipment pumps the metered and mixed product to the gun through, for example, 35 feet (about 11 meters) of hose. Since the product in the hose typically has only a one to three hour pot life, for example, it must be used or the hose must be flushed before the product hardens. Typical costs to flush a hose filled with mixed components in a 2K or 3K system are in the range of $0.50 U.S. per foot of hose (about $1.65 U.S. per meter of hose).
Many painters use pressure-feed guns to obtain large, that is, 10″ to 12″ (about 25 cm to about 30 cm or so), spray patterns. Newer gravity-feed cup-type guns can also spray that size pattern. In these devices, a reservoir, or cup, of the gun is filled with mixed 2K or 3K product from a metering system, and the mixed product is then dispensed from the gun. This eliminates much paint hose waste.
Ratio metering systems are typical of existing 2K and 3K dispensing equipment. The stroke of each pump in such equipment is adjustable to control the component ratios. Component pump mounting points are moved along a tilted plate, sometimes referred to as a rocker plate, to change the pumps' swept volumes, thereby adjusting the pumps' ratios. An air cylinder operates the pumps. There are also some systems that control the ratios electronically, such as, for example, the Ransburg E-Z Flow system.